She was the last Yonko to be named. Her epithet was first revealed just after the Battle of Marineford by Eustass Kid, and her real name was first mentioned by Pappug in the Fishman Island Arc.
Big Mom has only been seen partially from the shadows, but it is clear that she is an incredibly large and obese woman whose face appears to be larger than her body. She also has a very wide grin, long curly hair, large bulging eyes, and a round nose and cheeks.
Her dress code seems to consist of a pink dress with red polka dots and high-heels.
In all of her appearances, she's always seen drooling a large amount of saliva. She was also shown to have a ring on the thumb of her left hand.
Big Mom loves sweets as she makes all the islands under her protection pay her in whatever kind of candy they can produce. She seems to be obsessed with them to the point that she bases her likes and hates from them and would destroy a country all for the sake of sweets. In spite of that though, she did not lose her control when Luffy claimed to have eaten all of her candy. Although she does not seem greedy, Big Mom seems to have somewhat of a capitalist mindset. She also refers herself as "ore" , a masculine way of saying "I", instead of the feminine "watashi" that most other females use.
If anything, she strongly believes that a Pirate must accept no compromise for something they want, and without any delays. Pappug thinks she is protecting Fishman Island with a business perspective, since the deals made with the candy do qualify as racketeering, although she seems to prioritize sweets over money and treasure. From her point of view, pirates do not accept compromises as she even refused a proposal of money to repair two of her ships and in turn, double the amount of candy for a simple delay of two weeks.
It also appears that she is quite ruthless as she decided to burn a country down when they failed to make their sweet payment, disregarding any reason for the failure, under the reason that she hates people who cannot keep their promises. The Minister of the Left was struck with apprehension and fear when it was realized her payment could not be made that month.
She is infamous for decimating islands over slight infractions, and is very voracious and is almost always seen drooling to the point that, when Luffy offered her treasure, she believed that he expected her to eat it in place of the candy. It appears she may even eat some of her own subordinates if hungry enough, showing clear signs of cannibalism.
Crew
Her subordinates call her "Mama", and most seem to be afraid of her. Also, she is willing to eat her subordinates when she is hungry, showing she doesn't seem to care for their well-being very much. So far, only the unnamed three-eyed girl and Bobbin appear to be unafraid of her. Bobbin even had a friendly chat with Big Mom after returning to her at Whole Cake Island.
Protectorates
Given her capitalist mindset, Big Mom only seems to impart protection upon her chosen territories for as long as they can meet the demanded candy tribute and will not hesitate to have them destroyed if there is even a chance that they will not be able to pay. Also her definition of "protection" seems to just mean from pirates, as her crew stated that the rebellion on Fishman Island was none of their concern.
Enemies
Monkey D. Luffy
When Big Mom sent her subordinates to collect the candy from Fishman Island, Luffy talked to her via a Den Den Mushi claiming that he is responsible for the lack of candy. However, Big Mom easily saw through his lie. She refused to take the treasure that Luffy offered in place of candy but admired the Supernova for standing up to her; and so she decided to target Luffy instead of Fishman Island. In response, Luffy notes that leaving Fishman Island under the protection of someone who would destroy it on a whim was out of the question. Thus, he declared a war saying that he would defeat her in the New World and that he would make Fishman Island his own territory.
Caesar Clown
In the past, Caesar Clown made dealings with Big Mom. However, the rogue scientist swindled a large sum of money from her and fears retributions. When her crew attacked the Thousand Sunny to retrieve him, Caesar begged the Straw Hats to protect him from her wrath.